Being that Sandisk SDXC memory cards are currently available from Amazon, Newegg and on Ebay for well under $100, (under half Sandisk authorized reseller prices) how many of these cards are likely to be fakes? Has anyone ever tested such a cheap Sandisk 64gb class 10 card with h2testw?

Some of them will definitely be fakes but it's almost impossible to say how many.

Perhaps the best advice is to buy from sellers with high ratings, checking their ratings where they've sold such memory cards and follow the mantra that if it sounds too good to be true, it probably is.

Yes, I'm advising this from first-hand experience - I had purchased a 32GB flash drive on eBay that was no more than 64MB when I tested it with h2testw but the seller was co-operative and refunded me in full without any troubles.

Memory cards in general have been dropping in price quite drastically. As far as MSRP goes, it's manufacturer's SUGGESTED retail price. Stores can usually sell for much less, especially in the photography world.

As for Sandisk Extreme vs other cards:

I had a Transcend card die on me at the worst possible moment, basically AFTER taking 100s of photos at an event, and right in the middle of a mass. I was able to recover some of the photos, but a lot of them were corrupt and there was nothing that could be done, even with Transcend's recovery program (comes with their card reader). And the time I wasted switching cards was really bad. Thankfully I was only volunteering, and I had given proper disclaimers before, but if you intend of charging money for your services, invest in a very good card.

After a lot of research, I bought a couple of Sandisk extreme class 10 SDHC cards. As Rorschach mentioned they're not the only mfg of class 10 cards, but they are insanely durable. I read an article where one card spent over a month on the bottom of the ocean floor before being found, and the photos were still all there. I bought a couple of them almost 2 years ago, and they have worked flawlessly.

In my mind, the Sandisk Extreme is the army tank of cards. Sure, there are prettier, cheaper, and possibly even faster cards out there, but if you're going on the frontline of photography, that extra protection is worth the extra cost.

If you don't care so much about the safety of your images, then no worries. A 5$ memory card will work fine; most of the time.

When buying cards, dont look on the price. It is the only medium that holds your photos. I know it is easy to write and hard to read if you dont have money, but you can always buy better card with lower capacity.I can reccomend GoodRAM, Kingston, and Pretec, i used kingston for five years and never had a problem with any (currently have 3 sd and one CF card)